Bearer arrangement for printing press

ABSTRACT

Cooperating bearers for the printing and impression cylinders in a printing press are provided with oppositely inclined conical surfaces on the peripheries thereof, and the bearers on one of the cylinders are mounted for axial movement so that the conical surfaces of the bearers can be maintained in engagement with each other upon adjustment of the distance between the axes of the two cylinders. Biasing means in the form of hydraulic cylinders continuously urge the movable bearers in an axial direction so as to press the conical surfaces of the cooperating bearers together. Second biasing means in the form of springs urge the movable bearers in the opposite direction for separating the conical surfaces when the hydraulic cylinders are de-actuated. The conical surface of at least one of each pair of cooperating bearers is formed with a curve that is convex relative to the opposed conical bearer surface so that the two surfaces engage each other only along a narrow circumferential area so as to avoid scuffing due to a velocity differential across the width of the conical surfaces. A control system actuates the hydraulic cylinders automatically in response to movement of the printing cylinder toward the impression cylinder, and de-actuates the hydraulic cylinders automatically in the absence of a sheet to be printed, and prior to the printing cylinder tripping away from the impression cylinder.

Vir Singh et al.

3,732,813 May 15, 1973 BEARER ARRANGEMENT FOR PRINTING PRESS Primary ExaminerRobert E. Pulfrey Assistant Examiner-Paul T. Sewell Attorney Daniel H. Dunbar et a1.

[75] Inventors: Mahendra Vir 'Singh, Chicago;

Bruno B. Pasquinelli, Evergreen Park, both of Ill. [57] ABSTRACT t Cooperating bearers for the printing and impression [73] Asslgnee' fi f l z Corpora' cylinders in a printing press are provided with opl S mg positely inclined conical surfaces on the peripheries [22] Filed: Jan. 3, 1972 thereof, and the bearers on one of the cylinders are I mounted for axial movement so that the conical sur- [ZI] Appl' 214345 faces of the bearers can be maintained in engagement with each other upon adjustment of the distance 52 U.S. c1 ..101/216 101/247 between the axes of cylinders- Biasing means 51 Int. Cl. ..B4lf5/00 1341f 13/24 the form hydraulic cylinders mmmuously urge 58 Field of Search ..101/5 6 216 21 s the "mvable bearers in an axial as PmSs 101/247, 100/168 the conical surfaces of the cooperating bearers 192/85 74/191 together. Second biasing means in the form of springs urge the movable bearers in the opposite direction for separating the conical surfaces when the hydraulic [56] References C'ted cylinders are de-actuated. The conical surface of at UNITED STATES PATENTS least one of each pair of cooperating bearers is formed 4 with a curve that is convex relative to the opposed 1,338,347 4/1920 Wood ..lOl/2l6 i l bearer Sui-fa:e so that the two surfaces engage ga each other only alonga narrow circumferential area 2598726 6/1952 i f g OI/217 so as to avoid scuffing due to a velocity differential 2986086 5/1961 z ""IIIII across the width of the conical surfaces. A control 3 9 7 2 5 pi l i un 7 system actuates the hydraulic cylinders automatically 3,208,376 9/1965 Gates ..l0l/247X in response to movement of the printing cylinder 3,259,060 7/1966 Martin ..!Ol/247X toward the impression cylinder, and de-actuates the 3,285,083 11/1966 S g "74/191 hydraulic cylinders automatically in the absence of a 3,326,439 6/1967 Sarke ..226/l8l sheet to be primed, and prior to the priming cylinder tripping away from the impression cylinder.

8 Claims, 6 Drawing Figures If 1/ F' 1 I w i 1 ls ,i\ \\ii/1 1..1 ?1 2 a x 5 M fi I II i 2 b s a z 27 PATENTEBHAY 1 5191s SHEET 3 OF 3 BEARER ARRANGEMENT FOR PRINTING PRESS DESCRIPTION- OF THE INVENTION The present invention relates generally to printing presses and, more particularly, to an improved bearer arrangement for the blanket and impression cylinders of offset printing presses.

An offset printing press comprises a plate cylinder and an impression cylinder mounted for rotation about fixed axes and an intermediate blanket cylinder mounted for rotation about a movable axis so that it can be tripped to and from and also adjusted pressurewise relative to the plate and impression cylinders to obtain the necessary pressure or squeeze between the respective surfaces for printing.

Each of these cylinders has a gap in its peripheral surface to accommodate plate and blanket clamp means or grippers for conveying sheets through the nip between the blanket and impression cylinders. These gaps create a problem in that as they pass adjacent one another there is no contact between the printing surfaces and thus there is a sudden relief of pressure. As the leading edges of the gaps come together again there is a sudden increase in pressure and this intermittent pressure relationship causes vibrations and/or relative movement between the cylinders, thereby producing imperfections in the printed product which are referred to as pressure streaks."

The plate and blanket cylinders normally are provided with bearers at each end thereof and the respective printing surfaces of said cylinders are maintained at a level relative to the bearers such that proper impression pressure is obtained when the coacting bearers are in contact. This bearer-to-bearer contact serves to stabilize the plate and blanket cylinders as their gaps pass so that the sudden release and application of pressure has substantially no deleterious effect. It is difficult, however, to provide this bearer-to-bearer contact between the blanket and impression cylinders since the blanket cylinder must be adjustable relative to the impression cylinder to accommodate various thicknesses of the stock to be printed.

There have been numerous attempts to compensate or eliminate this condition, but most of these attempts have been only partially successful. In most known attempts to solve this problem, the corrective means have been applied to the cylinder journal housings and/or bearings for the purpose of taking up all looseness or play therein and this was helped to reduce the vibrations (e.g., see Siebke U.S. Pat. No. 2,986,86). In other instances, the corrective means have been applied to the cylinder journals between the frames and the cylinder body and here again some improvement was gained (e.g., see Sarke U.S. Pat. No. 3,326,439). However, in all of these cases the stabilizing means are applied near the ends of the cylinders and, therefore, they do not compensate for deflection of the cylinder body, and they severely complicate or completely preclude tripping the blanket cylinder to and from its printing position. In Stempel U.S. Pat. No. 2,598,726, a structure is described for providing bearers between blanket and impression cylinders, but that structure uses a resilient biasing element which detracts from the rigidity of the bearer arrangement, and which limits the range of adjustability.

It is a primary object of the present invention to provide an improved bearer arrangement for offset printing presses which maintains positive bearer-to-bearer contact contact between the blanket and impression cylinders under all circumstances, and yet does not interfere with, nor complicate, normal tripping of the blanket cylinder.

It is a further object of the invention to provide such an improved bearer arrangement which is fully automatic and self-compensating in that it adjusts the bearers automatically in response to relative movements of the corresponding press cylinders.

Another object of the invention is to provide such a bearer arrangement which restrains the cylinders in the axial direction as well as the radial direction.

A still further object of the invention is to provide such an improved bearer arrangement that is simple and economical to manufacture and maintain.

Still another object of the invention is to provide such an improved bearer arrangement which is readily adaptable to synchronization with the tripping mechanism.

Other objects and advantages of the invention will be apparent from the following detailed description and upon reference to the accompanying drawings in which:

FIG. 1 is an end elevation of the plate, blanket, and impression cylinders of an offset printing press embodying the invention;

FIG. 2 is an enlarged bottom plan, partially in section, of the impression and blanket cylinders of FIG. 1 with their associated drive and bearer arrangements;

FIG. 3 is an enlarged fragmentary section of one portion of the bearer arrangement shown in FIG. 2;

FIG. 4 is an enlarged fragmentary section of another portion'of the bearer arrangement shown in FIG. 2;

FIG. 5 is a diagram of the pneumatic control system associated with the blanket and impression cylinders and their bearers in the press of FIG. 1; and

FIG. 6 is a schematic diagram of the electrical control system associated with the blanket and impression cylinders and their bearers in the press of FIG. 1.

While the invention will be described in connection with certain preferred embodiments, it will be understood that it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalent arrangements as may be included within the spirit and scope of the invention. For example, we have elected to disclose our invention as incorporated on the blanket and impression cylinders of an offset printing press but it will be readily apparent that the concept is applicable to rotary letter presses, die cutting and creasing presses or other devices having coacting rotary members with gaps in their peripheries and which operate on materials of varying thicknesses.

Turning now to the drawings, and referring first to FIG. I, there are shown the conventional impression cylinder 10, blanket cylinder 11, and plate cylinder 12 of an offset printing press. The impression cylinder 10 and the plate cylinder 12 are mounted for rotation about fixed axes, while the intermediate blanket cylinder 11 is mounted for rotation about an axis that is movable with respect to the axes of the impression and plate cylinders 10 and 12, thereby enabling movement or tripping" of the blanket cylinder 11 toward and away from the impression and plate cylinders 10 and 12 and also adjustment of the pressure between the cooperating cylinders. The journalling means for the blanket cylinder has not been shown since it forms no part of the present invention but reference may be had to U.S. Pat. No. 2,568,761 for a typical and well known arrangement for adjusting and tripping such cylinder.

As shown more clearly in FIG. 2, the cylinders are all journalled in a pair of spaced frame members 13 and 14 and are driven by a train of gears such as 15 and 16 located outboard of the frame members. The longitudinal gap 17 in the surface of the impression cylinder can be seen in FIG. 2. As mentioned previously, this gap 17, which accommodates clamp means or grippers, may cause pressure streaks in the printed produce due to pressure variations caused by the gap 17 as it passes the corresponding gap in the blanket roll 11. To eliminate or at least minimize these pressure variations, a pair of bearers 18 and 19 are mounted on opposite ends of the impression cylinder 10 for cooperation with a corresponding pair of bearers 20 and 21 mounted on opposite ends of the blanket cylinder 11. These bearers have solid peripheral surfaces, without any gaps, which rid continuously on each other so as to provide a continuous bearing support for both cylinders 10 and 11 at opposite ends thereof.

In accordance with the present invention, the bearers for the blanket and impression cylinders have oppositely inclined conical surfaces on the peripheries thereof with at least one of the bearers in each pair being mounted for axial movement for maintaining the conical surfaces in engagement with each other upon radial displacement of the cylinders relative to each other, and biasing means continuously urge the movable bearer in each pair in an axial direction so as to press the opposite inclined conical surfaces together and maintain them in engagement with each other. Thus, in the illustrative arrangement, the outer periphcries of the two pairs of cooperating bearers 18, 20 and 19, 21 form oppositely inclined conical surfaces which ride on each other when the bearers are in engagement. The oppositely inclined conical surfaces tend to preclude relative movement of the cylinders in the axial direction, and also enable the bearers to be maintained in engagement with each other when the distance between the axes of the cylinders 10 and 11 is adjusted. Conical bearers have been used heretofore, as shown in Wood US. Pat. No. 1,338,347, but not in the manner in which they are used in the present invention.

To enable radial movement of one of the cylinders 10 and 1 1 relative to each other, while still maintaining the oppositely inclined conical surfaces of the corresponding bearers in engagement with each other, the two impression cylinder bearers l8 and 19 are mounted for axial movement relative to the two cooperating blanket cylinder bearers 20 and 21 and to the two cylinders 10 and II. The mounting arrangement is the same for each of the two axially movable bearers 18 and I9, and thus only one of them will be described in detail herein. Referring particularly to bearer 18, this bearer is guided or stabilized on the body of the cylinder journal and by four hollow support members 22 spaced at 90 intervals around the hub of the cylinder 10. As shown most clearly in FIG. 3, the inboard end of each support member 22 is slidably received within a bore 23 formed in the body of the cylinder 10, and the inner end of the support member 22 is rounded and flared outwardly as at 22a to facilitate sliding movement of the support member within the bore with a minimum of friction. The outboard end of each support member forms a tapered cavity which receives an expansion nut 24 for securing the support member 22 to the bearer 18.

For the purpose of continuously biasing the conical surface of the movable bearer 18 toward the oppositely inclined conical surface of the cooperating bearer 20, a pair of hydraulic cylinders 25 and 26 are mounted on opposite sides of each support member 22, with the inboard ends of the cylinders fitting into recesses formed in the outboard surface of the bearer 18. The cylinders 25 and 26 are connected through lines 27 and 28, respectively, to a regulated source of pressurized hydraulic fluid through a control system to be described in more detail below. To support the cylinders 25 and 26, as well as the other three pairs of hydraulic cylinders associated with the other three support members 22 for the bearer 18, all the hydraulic cylinders are secured to, and extend through, a retaining ring 29 fastened to the end of the cylinder 10 by means of four bolts 30 extending through the hollow interiors of the support members 22 and threaded into the body of the cylinder 10.

It will be understood that when hydraulic pressure is supplied to the cylinders 25 and 26, they urge the impression cylinder bearer 18 axially toward the cylinder 10 so as to urge the conical surface of the impression cylinder bearer 18 firmly against the oppositely inclined conical'surface of the cooperating bearer 20. When the hydraulic pressure is released, the bearer 18 is free to move away from the cylinder 10 so that the cylinder 10 can be moved closer to cylinder 11 with the conical surface of the bearer 18 riding downwardly over the conical surface of the bearer 20. Consequently, the bearers 18 and 20 can be maintained in engagement with each other for different radial positions of the two cylinders 10 and 11 relative to each other.

In order to move the bearer 18 axially away from the cooperating bearer 20 whenever hydraulic pressure is removed from the cylinders 25 and 26, a compressed coil spring 31 is mounted between the end wall of the bore 23 and the inboard end of each support member 22 so as to bias the bearer 18 axially against the bias of the hydraulic cylinders 25 and 26. Of course, the biasing against the bias of the hydraulic cylinders 25 and 25. Of course, the biasing force of the springs 31 is overcome by the hydraulic pressure of the cylinders 25 and 25 whenever the cylinders are actuated, but when the cylinders 25 and 26 are de-actuated by removing the hydraulic pressure therefrom, the spring 31 becomes effective to move the bearer 18 in the outboard direction.

In accordance with one particular aspect of the present invention, at least one bearer in each cooperating pair of bearers is mounted for circumferential movement relative to the cylinder on which that bearer is mounted. As can be seen most clearly in FIG. 4, the angular velocity of the outer periphery of the bearers 18 and 20 will vary with different axial positions of the movable bearer 18. On the other hand, the surface velocity of the cylinders 10 and 11 remains constant, so there is necessarily a difference between the velocity of the cylinders and the velocity of the bearers, as the axial position of the movable bearer 18 is changed. Consequently, the bearer 20 is mounted for circumferential movement relative to the cylinder 11. More specifically, the bearer 20 is mounted between a pair of thrust bearings 32 and 33, and rides on a set of needle bearings 34 so that the bearer 20 is free to move in the circumferential direction relative to the blanket cylinder 11 and the bearer 35 which cooperates with a bearer on the plate cylinder, while at the same time providing bearings support for the cylinder 11 in both the radial and axial directions.

As still another feature of the present invention, the conical surface of at least one bearer in each pair of cooperating bearers is formed with a curve that is convex relative to the opposed conical bearer surface so that the two conical surfaces engage each other along only a narrow circumferential area in any axial position of the movable bearer. Thus, as can be seen most clearly in FIG. 4, the inboard edge of each conical bearer surface will have a velocity slightly different from the outboard edge of that same conical bearer surface. Consequently, if the conical bearer surfaces were to engage each other across the entire width thereof, scuffing of the bearer surfaces would result due to the velocity differential across the width of the bearer surfaces. Accordingly, the conical surface of the bearer is curved so that it is convex relative to the cooperating surface of the bearer 18, thereby providing only a narrow line of contact between the two bearer surfaces. This line of contact is sufficiently narrow that there is no substantial velocity differential thereacross, and thus there is not scuffing of the cooperating bearer surfaces.

In accordance with a further aspect of the present invention, the biasing means for the movable bearers are actuated in timed relation to the tripping of the blanket cylinder toward and/or away from the impression cylinder. Thus, in the illustrative control system illustrated in FIGS. 5 and 6, the hydraulic pressure supplied to the hydraulic cylinders such as and 26 which bias the movable bearers 18 against the opposed bearers 20 is controlled by the hydraulic pressure in an output line 36 leading from an hydraulic intensifier 40 (FIG. 5). When printing is to start, the operator actuates a pressure handle to close switches SW1 and SW2 (FIG. 6). The closing of switch SW1 energizes a relay coil CR1 thereby closing contacts CRla to energize solenoid S1, while the closing of switch SW2 energizes solenoid S2 at the same time. The energization of solenoids S1 and S2 opens the two corresponding solenoid-operated air valves 41 and 42 (FIG. 5), with valve 41 supplying air to two conventional trip cylinders 43 and 44 which control conventional mechanism for tripping of the blanket cylinder toward and/or away from the impression cylinder. Although the air valve 42 is opened at the same time, air does not pass through this valve because the air supplied thereto from the source is stopped by normally closed spool valves 45 and 46 which are adapted to be actuated by movement of levers, not shown, which comprise elements of the blanket cylinder trip mechanism. As the press is tripped on, i.e., the blanket cylinder is moved to its printing position relative to the plate and impression cylinders in response to the opening of valve 41, the movement of the trip mechanism levers to their on positions, causes the mechanical spool valves 45 and 46 to open and to supply air to the previously opened valve 42 and on through valve 42 to the hydraulic intensifier 40, thereby producing pressure in the hydraulic output line 36 for actuating the biasing cylinders 25 and 26 topress the movable bearers 18 and 19 into firm engagement with the cooperating bearers 20 and 21. The air pressure in the line leading from valve 42 to the hydraulic intensifier may be house air at a pressure of about to p. s. i. which is transformed by the intensifier to hydraulic pressure of about 800 to 900 p. s. i. in the line 36. This pressure obviously may be regulated to produce the pressure desired between the coacting bearers. As the biasing force is applied to the movable bearers 18 and 19, a pressure switch PS1 closes in response to the pressure change'in the output line 36 from the intensifier 40, for a purpose to be described below.

In accordance with still another particular aspect of the invention, the biasing means for the movable bearers are de-actuated in response to the detection of the absence of a sheet to be printed. Thus, if a conventional sheet detector on the register table of the press, for example, senses the absence of a sheet at a specific time in the cycle'of operation, it will open the switch SW2, thereby also opening switch SW1 which is mechanically coupled to the SW2. When switch SW1 is opened, the relay coil CR1 is de-energized to open contacts CRla and thereby de-energize solenoid S1. This closes the solenoid operated air valve 42 so as to cut off the supply of air pressure to the hydraulic intensifier 40 whereupon the pressure in line 36 is rapidly exhausted through a quick exhaust valve 47. As the pressure in line 36 is reduced, the biasing cylinders 25 and 26 for the movable bearers are de-energized so that the movable bearers are biased away from the cooperating bearers by the springs 31.

When the switch SW2 is opened in response to the detection of a no sheet condition on the register table, the solenoid S2 remains energized through the closed pressure switch PS1. Consequently, the solenoid-operated air valve 41 remains open until the pressure switch PS1 is opened in response to a reduction in the pressure in the output line 36 from intensifier 40, following the closing of valve 42. When pressure switch PS1 is opened, the solenoid S2 is de-energized so as to close the valve 41 and thereby cut off air pressure to the trip cylinders 43 and 44. These trip cylinders 43 and 44 are spring biased so that they automatically actuate attached trip dog levers which, in turn, cause the blanket cylinder to trip of when the valve 41 is closed. Thus, it can be seen that the de-energization of solenoid S2 is delayed for a short interval following the de-energization of solenoid S1 so that the blanket cylinder is not tripped off until the biasing effect of the hydraulic cylinders 25 and 26 is removed from the movable bearers 18. When the blanket cylinder is tripped off," the trip dog levers also move away from the spool valves 45 and 46 to allow these valves to return to their normally closed conditions.

In the electrical portion of the control system illustrated in FIG. 6, a second pair of solenoids S3 and S4 are shown for controlling the trip actuating cylinders and bearer actuating cylinders of a subsequent multicolor unit. These solenoids S3 and S4 control a pair of solenoid operated air valves which function in the same manner as the valves 41 and 42 described above and shown in FIG. 5. However, the energization of the solenoids S3 and S4 is controlled by a pair of switches SW3 and SW4 which are adapted to be actuated by sheet detectors which may be located on a transfer cylinder or other mechanism which is employed to transfer sheets between units of a multicolor press. Consequently, as the first sheet passes through the first unit, its presence is detected by the sheet detectors for the next succeeding unit which cause the switches SW3 and SW4 to close. This energizes the solenoids S3 and S4 to trip on the blanket cylinder of the subsequent multi-color unit in the same manner described above for the first unit, closing switch PS2 in the process. When the absence of a sheet is detected by the sheet detectors, the switches SW3 and SW4 are opened to de-energize the solenoids S3 and thereby de-actuate the hydraulic cylinders associated with the movable bearers. As the hydraulic cylinders are de-actuated, the pressure switch PS2 is opened, thereby actuating mechanism which causes the blanket cylinder of the subsequent multi-color unit to trip off in the same manner described above for the first unit. If three or more units are involved in the press, each unit is provided with its own sheet detectors and switches and solenoids corresponding to the switches SW3, SW4, PS2 and solenoids S3, S4.

As can be seen from the foregoing detailed description, this invention provides an improved bearer arrangement which maintains positive bearer-to-bearer contact between the blanket and impression cylinders under all circumstances, and yet does not interfere with, nor complicate, normal tripping of the blanket cylinder. This improved bearer arrangement is fully automatic and self-compensating in that it adjusts the bearers automatically in response to relative movements of the corresponding press cylinders. Furthermore, the conical surfaces on the cooperating bearers restrain the cylinders against relative movement in the axial direction as well as the radial direction. This improved bearer arrangement is simple and economical to manufacture and maintain, and is readily adaptable to synchronization with the tripping mechanism.

We claim as our invention:

1. In a printing press, the combination of a printing cylinder and a cooperating impression cylinder having parallel axes and mounted for adjustment of the distance between said parallel axes, cooperating bearers mounted on said cylinders at opposite ends thereof with the bearers of the respective cylinders having inclined conical surfaces on the peripheries thereof and engaging each other, the bearers on at least one of said cylinders being mounted for axial movement relative to said one cylinder for maintaining said conical surfaces in engagement with the coacting bearers on the other one of said cylinders upon adjustment of the distance between the axes of said cylinders, and fluid power means connected between said one cylinder and the movable bearers thereon for continuously urging each said movable bearer in an axial direction so as to maintain contact with the oppositely inclined conical surface of its coacting bearer on the other one of said cylinders under a predetermined pressure.

2. In a printing press, the combination of claim 1 in Which the bearers on the said other one of said cylinders are mounted for circumferential movement relative to said cylinder.

3. In a printing press, the combination of claim 2 in which bearing means are provided for the bearers on the said other one of said cylinders to permit circumferentialmovement of said bearers relative to said cylinder.

4. In a pring press, the combination of claim 1 in which said fluid power means comprises a plurality of hydraulic cylinders acting on said movable bearers.

5. In a printing press, the combination of claim 1 which includes resilient spring means for urging each movable bearer in an axial direction opposite that of the fluid power means for separating said oppositely inclined conical surfaces, the force of the resilient spring means being substantially less than the force of the fluid power means so that the resilient spring means is effective only when the fluid power means is ineffective.

6. In a printing press, the combination of claim 1 which includes trip mechanism for moving the printing cylinder toward and away from the impression cylinder, and means for actuating said fluid power means in response to movement of said printing cylinder toward said impression cylinder.

7. In a printing press, the combination of claim 1 which includes sensing means for detecting the presence or absence of a sheet to be printed, and control means responsive to said sensing means for deactuating said fluid power means in the absence of a sheet to be printed.

8. In a printing press, the combination of claim 7 which includes means responsive to the de-actuation of said fluid power means for moving said printing cylinder away from said impression cylinder.

P0405) UNITED STATES PATENT OFFICE CETWEQATE Q15 CORRECTION Patent No. 3, 732 813 Dated May 15, 1973 Inventor(s Mahendra Vir Singh and Bruno B. Pasquinelli It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line numbered 49, change "was" to --has--;

line numbered 50, change "2,986,86" to "2,986,086".

Column 3, line numbered 21, change "rid" to ride--.

Co1umn 4, line numbered 42, delete "Of course, the bias-" line numbered 43, delete entire line line numbered 44, delete "25 line numbered 46, change "25" to --26--.

Column 8, line numbered 17, change "pring" to -printing--.

Signed and sealed this 23rd dag, f April 1974-.

(SEAL) Attest:

EDWARD 1-l.F'LiiTChER,JR. C. MARSHALL DALE-I Attesting Officer Commissioner of Patents 

1. In a printing press, the combination of a printing cylinder and a cooperating impression cylinder having parallel axes and mounted for adjustment of the distance between said parallel axes, cooperating bearers mounted on said cylinders at opposite ends thereof with the bearers of the respective cylinders having inclined conical surfaces on the peripheries thereof and engaging each other, the bearers on at least one of said cylinders being mounted for axial movement relative to said one cylinder for maintaining said conical surfaces in engagement with the coacting bearers on the other one of said cylinders upon adjustment of the distance between the axes of said cylinders, and fluid power means connected between said one cylinder and the movable bearers thereon for continuously urging each said movable bearer in an axial direction so as to maintain contact with the oppositely inclined conical surface of its coacting bearer on the other one of said cylinders under a predetermined pressure.
 2. In a printing press, the combination of claim 1 in which the bearers on the said other one of said cylinders are mounted for circumferential movement relative to said cylinder.
 3. In a printing press, the combination of claim 2 in which bearing means are provided for the bearers on the said other one of said cylinders to permit circumferential movement of said bearers relative to said cylinder.
 4. In a pring press, the combination of claim 1 in which said fluid power means comprises a plurality of hydraulic cylinders acting on said movable bearers.
 5. In a printing press, the combination of claim 1 which includes resilient spring means for urging each movable bearer in an axial direction opposite that of the fluid power means for separating said oppositely inclined conical surfaces, the force of the resilient spring means being substantially less than the force of the fluid power means so that the resilient spring means is effective only when the fluid power means is ineffective.
 6. In a printing press, the combination of claim 1 which includes trip mechanism for moving the printing cylinder toward and away from the impression cylinder, and means for actuating said fluid power means in response to movement of said printing cylinder toward said impression cylinder.
 7. In a printing press, the combination of claim 1 which includes sensing means for detecting the presence or absence of a sheet to be printed, and control means responsive to said sensing means for de-actuating said fluid power means in the absence of a sheet to be printed.
 8. In a printing press, the combination of claim 7 which includes means responsive to the de-actuation of said fluid power means for moving said printing cylinder away from said impression cylinder. 